Expressional characterization of dehydroascorbate reductase cDNA in transgenic potato plants

Abstract

In plants ascorbic acid (AsA) is a strong antioxidant or reductant that can be converted to dehydroascorbate (DHA) by oxidation. DHA, a very short-lived chemical, can either be hydrolyzed irreversibly to 2,3-diketogulonic acid or recycled to AsA by dehydroascorbate reductase (DHAR). DHAR cDNA, isolated from sesame hairy roots, was inserted into two plant expression vector systems with the CaMV35S promoter (CaMV35S::DHAR) and a potato tuber-specific promoter, Patatin (Patatin::DHAR). Southern and northern blot hybridization analyses indicated that DHAR cDNA was successfully integrated into the potato genome and actively transcribed. High levels of sesame DHAR transcript and DHAR enzyme activity were determined, by the Patatin promoter, in regenerated potato tubers, but their levels in leaves were very low. In contrast, much higher amounts of transcript were accumulated in the leaves of CaMV35S::DHAR regenerants than in the tubers while the activity of DHAR enzyme was higher in the latter. AsA content in the tubers of Patatin::DHAR transgenic lines was also increased (1.1. to 1.3-fold) cor~pared with that of non-transgenic plants. However, this was not true for the transgenic leaves. In contrast, the CaMV35~ promoter was associated with AsA accumulations in both the tubers (up to 1.6-fold) and the leaves (up to 1.5-fold). Howevel. more detailed analyses indicated that this increased enzyme activity was not always accompanied by an elevation in AsA .c(~ntent from transgenic plants. This suggests that other factors may limit the accumulation of vitamin C via ascorbaterecycling; in transgenic potato plants.

Greater protection against oxidative damages imposed by various environmental stresses in transgenic potato with higher level of reduced glutathione

“…Higher reduced states of ascorbate were similarly reported in transgenic poplar trees with overexpressed GR from bacteria (Foyer et al 1995). Moreover, these results come on line with the recent findings that increased DHAR activity in transgenic potato was not always accompanied by elevation in AsA and other factors might limit AsA accumulation (Goo et al 2008).…”

“…Enhancement of oxidative stress tolerance have been reported in transgenic potato overexpressing Cu/Zn superoxide dismutase gene (Perl et al 1993), class II catalase (Yu et al 1999), both Cu/Zn SOD and ascorbate peroxidase (Tang et al 2006) and nucleoside diphosphate kinase 2 (Tang et al 2008). Recently, Goo et al (2008) have characterized the expression of DHAR gene in leaves of transgenic potato and suggested that increased DHAR activity was not always accompanied by elevation in AsA and other factors might limit accumulation of AsA.…”

Overexpression of the sweet potato IbOr gene results in the increased accumulation of carotenoid and confers tolerance to environmental stresses in transgenic potato

“…tumefaciens GV3101 bearing a recombinant vector as previously described [29,30]. Briefly, after cocultivation with A. Tumefaciens carrying recombinant vector, they transferred on a regeneration medium (MS salts, sucrose 30 g/L, NAA 0.01 mg/L, zeatin 2.0 mg/L, GA3 0.1 mg/L, carbenicillin 500 mg/L) and maintained until the regeneration of shoots.…”

Expression Profiles of Genes Involved in the Carotenoid Biosynthetic Pathway in Yellow-Fleshed Potato Cultivars (Solanum tuberosum L.) from South Korea

“…Upon their arrival, some of these tubers were immediately frozen with liquid N 2 for carotenoid analyses and reverse transcriptase polymerase chain reaction (RT-PCR). Others were maintained for in vitro propagation, in which the sprout meristem tissues were initially cultured in a liquid medium (4.4 g L −1 of basic Murashige and Skoog salts and 30 g L −1 of sucrose), then subcultured on a solid medium (8 g L −1 of phyto agar in liquid media) [18,25,39]. Three other cultivars-Jowon, Superior, and Dejima-were obtained from the National Institute of Highland Agriculture, RDA, South Korea in 2005 and have since then been maintained in vitro.…”